In color liquid crystal display devices of the in-plane field type, one or both of two transparent substrates placed opposite to each other, with a liquid crystal layer disposed in between, have display electrodes and reference electrodes arranged in areas on the sides of the liquid crystal corresponding to unit pixels, and an electric field parallel to the transparent substrate surface is produced between the display electrodes and the reference electrodes to modulate light passing through the liquid crystal layer.
Such a color liquid crystal display device can produce a picture that can be recognized at a wide viewing angle and has become known for its excellence in the so-called wide angle visual field.
Liquid crystal display devices with the above configuration are described in detail, for example, in the Published Japanese Translation of PCT International Publication for Japanese Patent Application No. 505247/1993, Japanese Patent Publication No. 21907/1988, and Japanese Patent Laid-Open No. 160878/1994.
It has been pointed out that liquid crystal display devices of this configuration, however, have a problem in that an undesired electric field produced from the video signal line changes the electric field between the display electrodes and the reference electrodes, causing so-called vertical smear extending along the video signal line on the display surface. A known means to solve this problem involves the use of a shield electrode on the same substrate close to the video signal line (see Japanese Patent Laid-Open No. 202127/1994).
Liquid crystal display devices thus structured, however, have a problem in that, because the shield electrode is provided on the same substrate, the capacitance between the shield electrode and the signal electrode is large, the load on the drive circuit becomes too heavy, and the power consumption or the size of the drive circuit becomes too large.
Liquid crystal display devices thus constructed have another problem in that, because opaque electrodes are formed like a comb, the percentage of the pixel area occupied by the opaque metal is high, and so the aperture ratio cannot be increased.
Further, because a voltage is applied to the reference electrodes formed in individual pixel areas through common stripe-shaped reference signal lines extending in a row or column direction, the waveform of the applied voltage becomes dull from the signal supply portions of the reference signal lines toward the far ends of the reference signal lines, with the result that a brightness gradient or so-called horizontal smear occurs with the reference signal lines on the display surface.
The present invention has been accomplished to avoid these circumstances and an object thereof is to provide a liquid crystal display device that minimizes so-called vertical smear and reduces power consumption and the size of the peripheral circuits.
Another object of this invention is to provide a liquid crystal display device having an improvement in the so-called aperture ratio.
Still another object of this invention is to provide a liquid crystal display device in which what is generally-called a brightness gradient and also the horizontal smear are suppressed.
A further object of this invention is to provide a liquid crystal cell with a low reflectance.